Interesting fact: A small room can quietly hold dozens of kilograms of air, even though it feels almost weightless when you walk through it.
The answer: At sea level, 1 cubic meter of dry air weighs about 1.2 kilograms, or around 2.6 pounds. Warm air is a bit lighter, while cold or high-pressure air is a bit heavier because density changes with conditions.
Air was once thought of as almost immaterial, but barometers and vacuum experiments in the 17th century proved it has pressure and mass. It is tricky to weigh because you are really weighing a defined volume under specific temperature, humidity, and altitude conditions. Knowing the weight of air matters in aviation, HVAC design, weather forecasting, and industrial ventilation.
